Embodiments of the present invention generally relate to apparatus and methods for testing packaging. More specifically, the present invention relates to apparatus and methods for testing packaging such as the integrity and/or seal strength of packaging, wherein one or more coatings are applied to one or more surfaces of the packaging prior to testing.
Many apparatus and methods have been created for packaging objects in impermeable membranes. In one simplistic form, apparatus have been created in the form of heat sealed pouches, containers, or envelopes for providing protection to moisture sensitive and/or sterile objects. In one such embodiment, packaging for protecting medical sutures during storage is provided. This packaging consists of two panels formed from a moisture impervious material such as aluminum foil. The aluminum foil is coated with a heat sealable resin such as polypropylene to further protect the sutures. The suture is placed between the two panels and heat is applied to the periphery of the panels to create a pocket for the suture in which such suture is protected from atmospheric moisture. The panels may additionally contain a tearing notch for simple removal of the sutures from the pocket.
Another similar apparatus for hermetically packaging food products is also known. For this apparatus, a package is formed by attaching a packaging film to the top of a container in which food is held. The packaging film includes an outer carrier layer, an inner heat-sealed layer, and a seal layer, wherein the heat-sealed layer is attached to the seal layer via an adhesive. Prior to heating, the three layers prevent the food product from losing moisture content and maintain the pressurization of the container. When the package is heated, pressure builds inside the container allowing the food product to be pressure-cooked. When a predetermined temperature and pressure are reached, the three layers become gas permeable allowing the container to self-vent, thereby preventing the package from bursting. Such packaging extends the shelf life of the food product and also allows food products to be heated quickly via pressure-cooking.
In addition, many systems and methods have been created to test the integrity of sealed packages such as the aforementioned packages. Such testing is important for preventing packaging failures such as seal failure, ingress of bacteria or other contaminants, and the like.
Many such systems and methods have been created in the form of gas chambers. Some such systems test the integrity of sealed packages having both gas permeable and non-gas-permeable portions. In one such system, the gas chamber contains a purge gas inlet, an outlet gas tube, and a tracer gas tube. The sealed package is placed within the gas chamber such that the gas-permeable portion is attached to a temporary barrier layer. The temporary barrier layer contains an aperture within its center that is aligned with the tracer gas tube. This aperture allows the tracer gas to permeate the sealed package via its gas-permeable portion. The non-gas-permeable portion of the package being test, as well as the point of attachment of the gas-permeable portion to the non-gas-permeable, are positioned within the chamber such that they do not physically contact the source of the tracer gas. Thereafter, a purge gas such as air or nitrogen is introduced into the chamber via the purge gas inlet. The purge gas is passed through the chamber and exits a vent in communication with the outlet gas tube such that no tracer or other gases remain within the chamber. Once the chamber is purged of all gases except the purge gas, the vent is closed and the purge gas source is shut off. An inert tracer gas such as carbon dioxide, helium, or neon is then introduced into the sealed package via the tracer gas tube and temporary barrier layer aperture. Gas within the chamber then exits the outlet gas tube and is transported to an analytical device such as a mass spectrometer. The concentration of the exiting gas is then analyzed to determine if any of the tracer gas was able to permeate the sealed package.
In a similar system, a gas chamber includes a conduit and an exhaust device in addition to a purge gas inlet, an outlet gas tube, and a tracer gas tube. This system functions in the same manner as the aforementioned system with the exception of the method for delivering the tracer gas. Although the tracer gas is introduced into the sealed package via the tracer gas tube and temporary barrier aperture, it is thereafter passed through the conduit to the exhaust device. This allows a continuous flow of tracer gas to enter the sealed package thereby providing more rapid delivery of the tracer gas. This increased delivery facilitates leakage, if leakage is to occur, thereby decreasing the time required to test the integrity of the sealed package.
Another known method of testing packaging is liquid dye testing. Some such methods are defined by the American Society for Testing and Materials International's (“ASTM”) Test Method F-1929. During such testing, the packaging is filled with liquid dye for a predetermined time period. A determination regarding the integrity and/or seal integrity of such packaging is determined based upon the leakage of such liquid dye through the packaging. However, the current use of liquid dye to test for seal defects in packages is messy and, due to the porosity of permeable packages, can lead to erroneous results.
Yet another known method of testing packaging includes testing via internal pressurization. Some such methods are defined by the ASTM's Test Method F-2096. This method tests for gross leaks (i.e., leaks greater than 250 μm) by placing the package to be tested underwater and inflating the package to a predetermined pressure. After the pressure has stabilized, the package is observed to ascertain whether any steady streams of bubbles are flowing therefrom. Such bubble streams, if any, evidence a gross leak.
In yet another known method of testing packaging is pressure decay testing. Some such methods are defined by the ASTM's Test Method F-2095. During such testing, the packaging is pressurized. After a predetermined time period, the pressurization of the packaging is tested to determine integrity and/or seal strength of such packaging. This method is capable of detecting leaks at a rate of 1×10−4 seconds and is designed to detect very small defects in packaging such as those responsible for bacterial contamination of the package. However, for permeable packages, the use of pressure decay testing is not possible due to the permeability of the package as the typical permeability of the package is an order of magnitude greater than the detectability required to perform such testing.
In many instances, the testing systems and methods discussed above have been limited to impermeable and/or non-porous materials and packaging since permeable and/or porous materials and packaging have been difficult to test due to the leakage caused by the normal permeability of such packaging. In most instances, permeable and porous materials and/or packaging are currently tested non-quantitatively for seal defects, integrity, and the like via subjective, visual inspections such as those prescribed in ASTM Test Standard F-1886.